Paper bag construction

ABSTRACT

A bag, for example, for dust collection in a vacuum cleaner, is comprised of a paper tube which is flattened at least at one end to there provide superposed paper plies and end edges of the paper plies are embedded in an elongated, self-supporting cap of thermoplastic material which extends across the flattened end of the tube and at least partly closes such end. The paper tube may have its end fully closed and sealed by the thermoplastic cap or the latter may merely restrict the opening of the bag end.

Feb. 13,1973

United States Patent 91 Terzuoli 300,876 11/1928GreatBritain..............1...........229/62 [54] PAPER BAG CONSTRUCTIONPrimary Examiner-D0nald F. Norton Attorney-Lewis H. Eslinger, AlvinSinderbrand and Curtis, Morris & Safiord h m 7 t n, E2 1 1 2 n v .fi o iH mm k 0 mm .m nt e me n DS m n e V n l l 6 7 .l.

[22] Filed: March 9, 1971 [57] ABSTRACT A bag, for example, for dustcollection in a vacuum [21] Appl. No.: 122,321

cleaner, is comprised of a paper tube which is flattened at least at oneend to there provide superposed paper plies and end edges of the paperplies are em- References Cited UNITED STATES PATENTS bedded in anelongated, self-supporting cap of thermoplastic material which extendsacross the flattened end of the tube and at least partly closes suchend. The paper tube may have its end fully closed and sealed by thethermoplastic cap or the latter may x merely restrict the opening of thebag end. 1/1962 Studley...............................229/62X FOREIGNPATENTS OR APPLICATIONS um V. mp DTF 008 566 999 11 1. .112 0453 -3000 806 367 5 3 3 0 2333 3 Claims, 1 1 Drawing Figures 1,094,702 12/1954France...................................229/62 ,PATENT'EDFEBU m53.716.181

' SHEEI 10? 5 QINVEN TOR oommcx TERZUOL-l BY ATTORNEY.

PATENIEDFEB 1 3 was 3.716; 181 SHEET 2 0F 5 IN VE N TOR DOMINICKTERZUOLI ATTORNEY Pmmmm 1 1m mi 3 OF 5 3.716. 181

xx x

INVENTOR INICK TERZUOLI DOM ATTORNEY.

SHEET k 0F 5 PATENTED FEB 1 3 ms IN VE N TOR B DOMINICK TERZUOLI 705FIG. 9.

ATTORNEY PATENTEU ran 13 ms SHEET 5 BF 5 IN VENTOR DOMINI CK TE RZ UOLIATTORNEY This invention relates generally to bags, such as, for example,disposable dust containers or filter bags for vacuum cleaners and to amethod and apparatus for producing such bags.

Disposable filter bags for vacuum cleaners are generally formed of paperor other fibrous flexible material which is porous. Such bags usuallyare closed at one or both ends and have opposing panels which areconnected at the sides of the bag by pleats or gussets to permitexpansion of the bag. Further, an aperture is provided either at an endof the bag or in one of the panels thereof for cooperation with the airinlet opening of the vacuum cleaner casing. Since bags of the describedcharacter are intended to be disposable, great emphasis is placed on thelow cost production thereof. Low cost production of the bags obviouslyrequires economical utilization of the fibrous flexible material formingthe bags, high speed operation of any machines that may be employed forthe bag production, and minimization of any manual labor.

In the production of bags of the described character, the fibrousflexible material is usually supplied in the form of a continuous web,for example, unwound from a roll thereof, and is moved continuouslyalong a predetermined path. During such movement of the web, adhesive isapplied along a longitudinal edge of the web and thereafter the web isfolded longitudinally upon itself so as to overlap and secure togetherthe longitudinal edge portions of the web by means of the previouslyapplied adhesive, thereby to form a tube. The folding operations furtherprovide the tube with opposed panels connected, at the sides, by pleatsextending longitudinally along the tube. The pleated'tube formed in theforegoing manner is transversely cut at locations spaced therealong toprovide separate tube sections intended to form respective bags.

ln forming a bag from each tube section, it is necessary to close atleast one of the ends of the tube section. One existing method ofclosing an end of the' tube section involves applying a stripe ofadhesive across an end portion of the tube section which is thereafterfolded over, for example, as in US. Pat. No. 3,276,192. In order toensure that both panelsof the folded over end portion of the tubesection will be adhesively secured, this method of closing a bag endrequires that the opposed panels of the pleated tube be cut along offsetlines when dividing the tube into tube sections. Although devices existfor effecting such cutting of the pleated tube during its continuousmovement in the longitudinal direction, such cutting devices have alimited practical operating speed, as do the devices provided forfolding over an end portion of each tube section after adhesive has beenapplied thereto, so that the rate at which the described bags can beproduced is accordingly restricted. Further, a closed bag end of thedescribed character is not wholly satisfactory in that the endportions'of the pleats in the folded over end portion of the bag are notadhesively secured to each other and thus permit the collected dust toseep therebetween.

In order to provide improved sealing of the bags at the closed endsthereof, it has been proposed to provide one or both of the ends of eachpleated tube section with'two or more transverse folds that areadhesively secured, for example, as in US. Pat. Nos.

2,779,255 and 3,479,802. However, the material required for the fold orfolds at one or both ends of the bag may represent as much as one-thirdof the total material required to produce the bag.

In another form of disposable filter bags for vacuum cleaners forexample, as disclosed in US. Pat. No. 2,909,238, one or both ends of thepleated tube sections are closed by means of a strip of gummed tapewhich is folded over the bag end to be closed, whereupon the taped endof the bag is folded over and adhesively retained in folded condition.Although this form of filter bag avoids some of the waste of materialrequired for the double-folded bag ends, there is no In still anotherform of dust containers or disposable filter bags for vacuum cleaners,one or both ends of the pleated tube sections are closed by stitchingthe same transversely thereacross and then further sealing each closedbag end by means of a strip of gummed tape which is folded over andcovers the stitching. Although this form of filter bag avoids the wasteof material required for the folded bag ends, there is again no overalleconomy, as the transverse stitching of the bag ends and the applicationof the gummed tape thereover cannot be conveniently effected while thetube sections continue to move at high speed.

In US. Pat. Nos. 3,333,523 and 3,361,334, I have proposed that the wasteof the fibrous sheet material resulting from the use of multiple foldsfor closing the ends of filter bags can be avoided by providing thesheet from which a bag of the described type is formed with a stripe ofadhesive extending completely across the face of the sheet which is atthe inside of the tube adjacent an end of the latter to adhesivelysecure together the pleats and panels at the end of the tube and therebyform a closed bag end. However, the tightness and reliability of theseal at the closed bag end depend upon the security of the adhesiveattachment of the panels and pleats to each other which requires theexertion of a sealing pressure for a substantial period,

Accordingly, it is an object of this invention to provide a bag havingopposed panels connected at the sides by pleats so as to be particularlysuited for use as a dust container or filter bag in a vacuum cleaner,which bag has one or both of its ends securely and tightly sealed in areliable manner that permits the high speed and economical productionthereof.

Another object is to provide a bag of the described character whichpermits the most economical utilization of the fibrous flexible materialfrom which the same is formed.

A further object is to provide a method and apparatus by which bagsparticularly suitable for use as disposable dust containers or filterbags of vacuum cleaners may be produced at a high rate ofspeed and in amost economical manner.

In accordance with an aspect of this invention, a sheet of flexiblefibrous material is folded upon itself and has its longitudinal edgessecured together in overlapping relation to form a tube having opposedpanels connected, at the sides, by pleats extending along the tube, thetube thus formed is cut transversely, at longitudinally spaced locationstherealong, into flattened tube sections, and each of the tube sectionshas an elongated, self-supporting enveloping cap of thermoplasticmaterial applied over at least one of its ends to seal or at leastpartly close the end embedded therein.

The enveloping plastic cap may be formed on an end of each flattenedtube section by dipping such end in a mass of the thermoplastic materialheated to a plastic state, or the plastic cap may be injection molded onthe end of the tube section. As a further alternative, the thermoplasticmaterial heated to a plastic state may be applied to the end of a tubesection by an applicator roller or rollers defining a recess throughwhich the end of the tube section is moved.

The above, and other objects, features and advantages of this invention,will be apparent in the following detailed description of illustrativeembodiments which is to be read in connection with the accompanyingdrawings, wherein:

FIG. 1 is a perspective view of one form of bag embodying thisinvention;

FIGS. 2 and 3 are enlarged, fragmentary sectional views taken along thelines 2-2 and 33, respectively, on FIG. 1;

FIG. 4 is a perspective view of another form of bag embodying thisinvention;

FIG. 5 is a schematic perspective view illustrating apparatus accordingto this invention for producing a bag, for example, as in the embodimentof FIG. 1;

FIG. 6 is a schematic perspective view showing another apparatusaccording to this invention for closing or sealing an end ofa bag;

FIG. 7 is an enlarged sectional view taken along the line 77 on FIG. 6;

FIG. 8 is a view similar to that of FIG. 6, but showing anotherapparatus according to this invention;

FIG. 9 is an enlarged sectional view taken along the line 99 on FIG. 8;

FIG. 10 is another view similar to that of FIG. 6, and showing stillanother apparatus according to this invention; and

FIG. 11 is an enlarged sectional view taken along the line l1l1on FIG.10.

Referring to the drawings in detail, and initially to FIG. 1 thereof, itwill be seen that a bag in accordance with this invention is formed of asheet of flexible material, such as, paper or other fibrous materialwhich is preferably porous when the bag is to be employed as adisposable dust container or filter bag for vacuum cleaners. The papersheet for forming the bag 20 is folded about longitudinal fold lines sothat its central portion forms a panel 21 connected, at its oppositesides, by pleats 22 with longitudinal edge portions 23:: and 23b,respectively. The portions 230 and 23b extend inwardly towards eachother so as to overlap at their edges, and such overlapping edges aresecured to each other by an adhesive stripe extending therealong. Itwill be seen that the folded sheet having its longitudinal edgesadhesively secured to each other forms a flattened tube having opposedpanels 21 and 23a, 23b connected, at the sides of the tube, by pleats 22extending along the tube. A bag may be formed from the flattened tubemerely by closing or sealing at least one end thereof.

In accordance with this invention, closing of an end of the flattenedtube is effected by embedding the adjacent end edge portions of panels21 and 23a, 23b and of pleats 22 in an elongated, self-supporting,enveloping cap 24 of thermoplastic material extending across the end ofthe tube which is to be closed (FIGS. 1, 2 and 3). Since the elongatedplastic cap 24 completely envelops the end edge portions of panels 21and 23a, 23b and of pleats 22, it will be apparent that the cap 24securely seals the end of bag 20 across which it extends, and therebyprevents seepage of dust from the closed end of bag 20 without resort tomultiple folds at the end of the bag. Such multiple folds, as previouslyemployed for closing the ends of dust containers or filter bags, requirea sheet of flexible material having a length up to one-third greaterthan the length of the finished bag, whereas the sheet for forming thebag in accordance with this invention'has a length equal to that of thefinished bag and therefore effects the most economic utilization of thesheet material. Since the plastic cap 24 is self-supporting and envelopsthe end edges of the sheet material or paper embedded therein, thereliability of the closure or sealing of the bag end is not dependentupon the adhesive attachment of plies of the fibrous sheet material toeach other, as in my previously mentioned US. Pat. Nos. 3,333,523 and3,361,334.

The bag shown on FIG. 1 is a disposable dust container or filter bag forvacuum cleaners of the type having one of its ends completely closed orsealed by the plastic cap 24 in the manner described above, while itsother end is only partly closed, that is, expansion of the pleats 22 atsuch other end is prevented, so that the partly closed end of the bagcan form an inlet opening closely receiving the vacuum cleaner inletthrough which dust laden air is supplied to the bag 20.

In accordance with the present invention, partial closing of bag 20 atthe end thereof which is to constitute the inlet opening for receivingdust laden air is effected by an elongated, self-supporting, envelopingcap 25 of thermoplastic material extending across such end of bag 20 andhaving the adjacent end edges of the panel 21 and the pleats 22 embeddedtherein and secured to each other by the cap 25, while the adjacent endedge of the other panel 23a, 23b is free of the plastic cap 25. Thus,cap 25 holds the pleats 22 closed at the respective end of the bag and arestricted opening is defined between the adjacent free edge of panel23a, 23b and panel 21.

Referring now to FIG. 4, it will be seen that the present invention canalso be employed for closing or sealing one end of a dust container orfilter bag 20 of the type having a rigid cardboard collar 26 adhesivelyattached to the opposite end of the bag and having an aperture (notshown) defining the inlet opening for the dust laden air. In accordancewith this invention, the end of bag 20' remote from the cardboard collaror disk 26 is tightly closed or sealed by an elongated, selfsupporting,enveloping cap 24 of thermoplastic material extending across such end ofthe bag and having the adjacent end edges of the panel 23a, 23'b, theside pleats 22' and the other panel (not shown) embedded in, and securedto each other by the cap 24.

Referring now to FIG. 5, it will be seen that bags having ends thereofclosed in accordance with this invention, as described above, may beproduced automatically and at a high rate of production in an apparatus30 employing, as the starting material, a continuous web W of sheetmaterial which is unwound from a supply roll R. The web W being unwoundfrom roll R moves continuously in the longitudinal direction and travelsaround a backup roller 31 which is suitably rotated and serves tosupport the web during the application of a longitudinal stripe ofadhesive to the web along one of its longitudinal edges by means of anadjacent adhesive applying device 32. As shown, the device 32 mayinclude a reservoir or tank 33 containing a supply of suitable adhesive,a pickup roller 34 rotatably supported to dip into the supply ofadhesive in reservoir 33, and a suitably driven adhesive applying wheel35 which is rotatably supported to effect peripheral rolling contactwith the surface of roller 34, for receiving adhesive from the latter,and with the web W on the backup roller 31.

After the longitudinal stripe of adhesive has been applied to the web,the latter moves continuously through a folding device 36 which may beof conventional type, as shown. Such folding device 36 generallyincludes upright guide posts 37 which are spaced apart by a distanceapproximately equal to the width of panel 21 of the finished bag, andwhich operate to upwardly bend the lateral portions of the web. Thedevice 36 further generally includes inner and outer pleating plates 38which are suitably supported, as at 39, and which act on the lateralportions of the web bent upwardly by posts 37 to form the pleats 22 andthe inwardly directed, overlapping portions 23a and 23b of the tube.

After the web W has been folded by device 36 into a continuous tube Thaving opposed panels connected, at the sides of the tube, by pleatsextending therealong, such tube passes between rollers 40 and 41 whichare suitably driven to pull the web through the folding device. Thedrive rollers 40 and 41 further press the tube flat and thereby achievesecure bonding of the overlapping edges of panel portions 23a and 23b bythe adhesive stripe between the overlapping edges. In order to cut thecontinuous flattened tube T into sections T' from which respective bagsare to be formed, apparatus 30 has a cutting device 42 disposed at alocation following drive rollers 40 and 41, and which may include afixed blade or anvil 43 disposed below the path of movement of the tubeand a rotary cutter 44 located above the flattened tube and cooperatingwith the anvil .43 to transversely shear the paper tube. The rotarycutter 44 is suitably driven so as to cut the paper tube when the lengthof the latter extending beyond the cutting edge of anvil 43 is equal tothe length of the bag to be formed.

The successive cut tube sections T' are delivered, either manually orotherwise, to an end of a conveyor table 45 along which they are movedduring the closing of an end of each of the tube sections. During suchmovement, the successive tube sections T extend transversely withrespect to the direction of their movement and each have an end portionE projecting laterally beyond a side edge 46 of the conveyor table. Themovement of tube sections T' along table 45 may be effected by a lowerconveyor belt 47 running around pulleys 48 and an upper conveyor belt 49running around pulleys 50. The pulleys 48 and 50 are suitably driven andmounted so that the upper run of belt 47 travels along the upper surfaceof table 45 in the direction away from the end of table 45 receiving thecut tube sections T', and the lower run of belt 49 bears downwardly onthe upper run of belt 47 and travels in the same direction. Thus, thesuccessive tube sections T are grasped between the confronting runs ofbelts 47 and 49 and carried over the surface of table 45.

As each tube section T' is transported along the surface of table 45,its projecting end portion E is bent downwardly by a suitably supportedguide bar 51 which extends along table edge 46 and is inclineddownwardly in the direction of movement of the tube sections. Anupwardly open tray or reservoir 52 is mounted below the side edge 46 oftable 45 and contains a mass 53 of a suitable thermoplastic materialwhich is maintained in its molten or plastic state by electric heaters54. The arrangement is such that, as the projecting end E of each of theconveyed tube sections T' is bent downwardly by guide bar 51, the endedge portion of the tube section dips into the molten mass 53 ofthermoplastic material in tray 52. As each conveyed tube section Treaches the end of guide bar 51 and is released by the latter, thedownwardly bent end portion E of the tube section tends to return to itshorizontal position by reason of the resiliency of the fibrous materialof which the tube section is formed, and such return of the end portionE of the tube section to'its horizontal position is assisted by alateral extension 55 of table 45 which projects beyond edge 46 aftertray 52. The lateral extension 55 of table 45 will of course tend tolift and support the end portions of the successive tube sections whichhad been previously bent downwardly by the guide bar 51. By reason ofthe dipping of the end edge portion of each tube section into the moltenmass 53 of thermoplastic material in tray 52, a relatively thick coatingor layer of such material adheres to and envelops the end edge portionwhen removed from the tray 52 and thereby forms the elongated plasticcap 24 for closing an end of each of the bags 20.

In the apparatus described above with reference to FIG. 5, the elongatedplastic cap 24 for closing an end of each bag is applied to therespective tube section T by the described dipping operation which isperformed during the continuous movement of the tube section by theconveyor belts 47 and 49. Thus, there is a continuous flow of materialthrough apparatus 30 from the supply roll R of the paper web to thedischarge end of conveyor belts 47 and 49 at which bags 20 having oneend closed or sealed are discharged from the apparatus.

Although the apparatus 30 described above forms the plastic cap 24 on anend of each bag by a clipping operation, it is apparent that the plasticcap can be formed on each bag in a number of other ways. For example, inthe apparatus illustrated on FIGS. 6 and 7, the plastic cap closing orsealing an end of each bag 20 in accordance with this invention isformed by an injection molding operation. More specifically, theapparatus 130 is shown to comprise a table 45 receiving the successivetube sections T which may be formed in the manner described withreference to FIG. 5, and conveyor belts 47 and 49 extending along table45 and by which the successive tube sections T are moved continuouslyalong the table. Each tube section, while conveyed, extends transverselywith respect to the direction of movement and is disposed with an endportion of the tube section projecting laterally beyond a side edge 46of the conveyor table. The apparatus 130 further comprises a moldingassembly 56 which is movable along a box-like track 57 extendingparallel to side edge 46 of the conveyor table.

The assembly 56 is seen to include upper and lower mold parts 58 and 59which are superposed and have mating recesses in their confrontingsurfaces to define a mold cavity 60 (FIG. 7). The lower mold part 59forms a carriage on which there are mounted rollers 61 and 62 in rollingcontact with the top surface and the opposed side surfaces of guidetrack 57 for movement of the assembly 56 along the guide track. Guideposts 63 (FIG. 6) are directed vertically upward from lower mold part 59and extend slidably through guide bushings 64 provided in upper moldpart 58, whereby the latter is movable vertically between a raisedposition (FIG. 6) in which the cavity 60 is open, and closed or loweredposition (FIG. 7) in which cavity 60 is closed and envelops an end of atube section T extending therein. A bracket 65 depends from lower moldpart 59 and supports a pneumatically operated cylinder 66 having apiston rod 67 projecting from its upper end and being secured by aclevis 68 and pin 69 (FIG. 7) to a bracket 70 extending from upper moldpart 58.

Flexible hoses 71 and 72 extend from a solenoid controlled valve 73 tothe lower and upper ends, respectively, of cylinder 66 for alternatelysupplying and exhausting hydraulic or other fluid under pressure to andfrom the cylinder. The solenoid controlled valve 73 has a conduit 74extending thereto from a source (not shown) of the fluid under pressureand a conduit 75 extends from the valve back to such source. Solenoidvalve 73 is of a conventional type designed so that, upon energizationof the valve, fluid under pressure is supplied to the upper end ofcylinder 66 through hose 72 and exhausted from the lower end of thecylinder through hose 71, whereby cylinder 66 moves mold part 58downwardly to close cavity 60. On the other hand, when solenoid valve 73is deenergized, fluid under pressure is supplied to the lower end ofcylinder 66 through hose 71 and exhausted from the upper end of thecylinder through hose 72, whereby cylinder 66 raises mold part 58 toopen the mold cavity.

When cavity 60 is closed with an end edge portion of a tube section Textending into the mold cavity, as shown particularly on FIG. 7, athermoplastic material in molten state is supplied to the closed cavity60 through a flexible feed conduit 76 which extends from a conventionalplastic pump (not shown) associated with a source of the plasticmaterial. The feeding of a predetermined quantity of the molten plasticmaterial to cavity 60 is suitably controlled so as to occur only whensuch cavity is closed. The mold cavity 60 is suitably dimensioned sothat it corresponds to the elongated cap 24 which is to be molded inenveloping relation to the end of the tube section T extending into themold cavity. During the molding of the cap 24 about the end edge portionof a tube section T, the latter is continuously moved by the conveyorbelt 47 and 49 and, therefore, molding assembly 56 is moved with tubesection T during the molding of a plastic cap 24 on the latter.

ln order to effect such movement of mold assembly 56, apparatus 130 hasa drive chain 77 (FIG. 6) running around sprockets 78 and 79 which arelocated adjacent the opposite ends of guide track 57 so that the upperrun of chain 77 will extend longitudinally through the guide track. Aconnecting member 80 depends from lower mold part 90 and extends througha longitudinal slot 81 formed along the top of guide track 57. As shownon FIG. 7, the connecting part 80 is suitably attached, as at 82, to theupper run of chain 77, whereby mold assembly 56 is moved in thedirection of movement of the successive tube sections, as indicated bythe arrow 83 on FIG. 6, in response to the rotation of sprocket 78 inthe counterclockwise direction. Conversely, mold assembly 56 is moved inthe return direction, as indicated by the arrow 84, in response to therotation of sprocket 79 in the clockwise direction.

In order to control the movements of mold assembly 56, sprocket 78 ismounted for rotation on a shaft 85 and is rotatably coupled to thelatter only upon energization of an electrically actuated clutch 86.Shaft 85 is rotated through a gear 87 fixed thereon and meshing with anidler gear 88 which, in turn, meshes with a gear 89 rotating with pulley48. The gears 87, 88 and 89 are dimensioned so that, upon the energizingof electric clutch 86, mold assembly 56 will be driven in the directionof the arrow 83 at the same speed as the conveyed tube section T.

The other sprocket 79 is freely rotatable on a shaft 90 and is rotatablycoupled to the latter only upon energization of an electric clutch 91.The shaft 90 is rotated, for example, through a pulley and belttransmission 92, by a drive shaft 93 rotated, for example, by anelectric motor 94. The arrangement is such that, when electric clutch 91is energized, sprocket 79 is rotated in the clockwise direction for thereturn movement of mold assembly 56 in the direction of arrow 84 at ahigh speed.

Limit switches 95 and 96 are suitably mounted at spaced apart locationson guide track 57 and are engageable by mold assembly 56, for example,by the connecting member 80 thereof, so as to limit the movement of themold assembly in the directions of the arrows 83 and 84, respectively.Additional limit switches 97 and 98 are mounted adjacent the edge 46 ofconveyor table 45 at suitably spaced apart locations so as to beengageable by the projecting end portions of tube sections T conveyedalong such table. The several switches 95-98 are included in suitableelectric control circuits (not shown) for automatically controlling theseveral operations by which the apparatus molds an enveloping cap 24 onan end edge portion of each of the tube sections. More specifically,when switch 98 is engaged by a tube section T delivered to table 45 andcommencing its movement along the table by conveyor belts 47 and 49,such engagement of switch 98 is effective to cause the energizing ofelectric clutch 91 so that mold assembly 56 is rapidly returned in thedirection of arrow 84 to a position at which such mold assembly engagesswitch 96 and thereby deenergizes clutch 91. When the tube section T isfurther conveyed and engages switch 97, such engagement of the switchcauses energizing of electric clutch 86 and also energizing of solenoidvalve 73. The location of switch 97 is selected in relation to thelocation of switch 96 so that engagement of the switch 97 by a tubesection T will occur when an end edge portion of such tube sectionextends into the open mold cavity 60 of the mold assembly 56 at itsreturned position defined by switch 96. Thus, upon engagement of switch97 by a tube section, mold assembly 56 will be moved with the conveyedtube section extending into its mold cavity 60, and such mold cavitywill be closed. Upon the closing of the mold cavity 60, the pump orother source of supply of the molten thermoplastic material can besuitably energized to inject a measured quantity of the thermoplasticmaterial into the closed cavity. When the mold assembly 56 reaches theend of its forward travel in the direction of the arrow 83 and engagesswitch 95, such engagement of switch 95 is effective to causedeenergizing of electric clutch 86 and also of solenoid valve 73 so thatthe forward movement of the mold assembly is halted and the mold cavity60 is opened to permit the removal of the molded cap 24 from the moldcavity and the continued movement of the molded cap with the tubesection T on which it has been molded.

The mold assembly 56 is thereafter returned in the direction of thearrow 84 to its starting position when the tube section next deliveredto the table 45 comes into engagement with the switch 98.

In the apparatus 30 of FIG. 5, each enveloping cap 24 formed on an endof a tube section T' by dipping operation is unconfined during itsformation, whereas, in the apparatus 130 of FIGS. 6 and 7, eachenveloping cap 24 is fully confined in the mold cavity 60 during itsformation. However, as shown on FIGS. 8 and 9, an apparatus 230according to this invention may only partly mold or confine the materialconstituting each cap 24 during the formation thereof on the end of atube section T. In the apparatus 230, the successive tube sections T'are again delivered to a conveyor table 45 and conveyed along the latterby belts 47 and 49 with each tube section extending laterally on thetable and having an end portion projecting laterally beyond the tableedge 46. The apparatus 230 is shown to further comprise a device 99mounted adjacent the side-edge 46 of table 45 and being operative toapply a thermoplastic cap 24 to each of the tube sections as the latterare conveyed past device 99. Such device 99 is shown to include upperand lower reservoirs 100 and 101 containing masses of thermoplasticmaterial and which are preferably provided with electric heaters (notshown) to maintain the thermoplastic material in a molten or plasticstate. Further, a supply conduit 102 may extend to upper reservoir 100from a source of the thermoplastic material for replenishing the supplyin the upper reservoir. A lower applicator reel or roller 103 mounted ona horizontal shaft 104 dips into the supply of plastic material in lowerreservoir 101 and has a stepped surface providing a large diameterportion 103a and a small diameter portion 103b (FIG. 9). An upperapplicator wheel or roller 105 is mounted on a horizontal shaft 106 andalso has a stepped surface to provide a large diameter portion 105a anda small diameter portion 105b. Shafts 104 and 106 are suitablyjournalled in a support frame 107 so that the large diameter portions103a and 105a of the applicator rollers are in rolling contact with eachother, and a recess 108 (FIG. 9) is defined between the small diameterroller portions 103b and 105b and is located for the Ill passage of endedge portions of the successive conveyed tube sections T through suchrecess 108. A transfer wheel or roller 109 is rotatably mounted on upperreservoir so as to dip into the supply of plastic material in thelatter, and such transfer roller 109 is of stepped configuration toprovide small and large diameter portions which respectively engage andtransfer plastic material to the large and small diameter portions ofapplicator roller 105. Preferably, applicator rollers 103 and are eachprovided with an electrical heating element 110 (FIG. 9) so as tomaintain the thermoplastic material in molten or plastic condition onthe applicator rollers. The current for energizing the electricalheaters 110 can be supplied thereto by way of conductors 111 extendingthrough the respective shafts 104 and 106 from slip rings 112 (FIG. 8)provided on end portions of such shafts. The applicator rollers 103 and105 are preferably driven in synchronism with the movement of tubesections T', for example, by a drive shaft 113 connected to theconveyordrive (not shown) and carrying a gear 114 meshing with a gear115 on shaft 104, and further by meshing gears 116 and 117 on shafts 104and 106. It will be apparent that, as an end edge portion of each tubesection T' moves through recess 108, the molten thermoplastic materialsupplied to rollers 103 and 105 from reservoirs 100 and 101 and coatingthe surfaces of such rollers 103 and 105 will be applied to the end edgeportion of the tube section with the thiclcness and extent of theapplied thermoplastic material being determined by the recess 103. Aseach tube section T moves away from rollers 103 and 105, thethermoplastic material applied by the applicator rollers will set andthereby form the enveloping cap 24 for sealing the end of the tubesection.

Referring now to FIGS. 10 and 11, it will be seen that, in the apparatus330 according to the invention, as there illustrated, each of the tubesections T, while being conveyed along the table 45 by conveyor belts 47and 49, has thermoplastic material, in a plastic or molten state,applied to an end edge portion of the tube section by a device 118 thatis fixedly mounted adjacent the edge 46 of the conveyor table. Thedevice 118 is shown to include a supporting frame 119 carrying areservoir 120 which contains a supply of the thermoplastic materialmaintained in a molten or plastic state by electric heaters 121. A motordriven pump 122 withdraws molten plastic material from reservoir 120 anddischarges the same through a spout 123 onto the surface of a transferwheel 124 which is rotatably carried by a vertical shaft 125 journalledin frame 119. The transfer wheel 124 engages at its periphery in thegrooved periphery 126 of an applicator wheel or roller 127 carried by avertical shaft 128 also journalled in frame 11.9. It will be seen thatthe grooved periphery 126 of the applicator wheel defines a recess 108'through which the end edge portions of the successively conveyed tubesections T travel during movement past the device 118.

As in the embodiment described with reference to FIGS. 8 and 9, therollers 124 and 127 preferably contain electric heaters 110' which areenergized through conductors 111 extending through the respective shafts125 and 128 from slip rings 112' (FIG. 10) provided on the upper endportions of the shafts. Further, the rollers or wheels 124 and 127 arepreferably rotated in synchronization with the movement of the tubesections, for example, by a drive shaft 113 driven from the conveyordrive (not shown) and carrying a gear 114 meshing with a gear 116' onshaft 125 which, in turn, meshes with a gear 117' on shaft 128. It willbe apparent that, as wheels 124 and 127 are thus rotated, the moltenthermoplastic material delivered to the surface of transfer wheel 124 bypump 122 will coat the surfaces of applicator wheel 127 and the recess108' defined by the grooved periphery of the applicator whee-l willdetermine the extent to which the thermoplastic material on the surfaceof the applicator wheel is applied to the edge portion of each tubesection T.

It will be seen that, in each apparatus provided according to thisinvention, the thermoplastic material is applied only to exteriorsurfaces and edge portions of each tube section T while the latter is inits flattened condition. The sealing or partial closing of an end of thetube section is effected by the mass of the thermoplastic material thusapplied, rather than by the use of an adhesive or thermoplastic materialfor causing adherence to each other of fibrous surfaces of the tubesection. In all of the embodiments of this invention described above,there is no necessity to maintain a sealing pressure on an end of eachtube section T for a long period of time in order to ensure the adequateadherence of the fibrous surfaces to each other.

Although illustrative embodiments of this invention have been describedin detail herein with reference to the accompanying drawings, it is tobe understood that the invention is not limited to those preciseembodiments, and that various changes and modifications may be effectedtherein by one skilled in the art without departing from the scope orspirit of this invention.

What is claimed is:

l. A bag comprising a paper tube which is flattened at least at one endand includes first substantially flat opposed panels connected at theirsides by second opposed panels which are creased to define pleatsdirected inwardly between said first panels at least at said flattenedend, and an elongated, self-supporting enveloping cap of thermoplasticmaterial extending across said one end and having adjacent end edges ofone of said first panels and said pleats embedded in, and secured toeach other by said cap, the other of said first panels having its endedge at said one end of the tube spaced, in the longitudinal directionof the tube, from said adjacent end edges of said one first panel andsaid pleats so that said end edge of said other first panel is free ofsaid thermoplastic cap and the latter holds said pleats closed at therespective end of said tube for providing a restricted opening to thebag.

2. A bag according to claim 1, in which end edges of both of said firstpanels and all of said pleats at the other end of said tube are embeddedin an additional elongated, self-supporting enveloping cap ofthermoplastic material which extends across said other end of the tubefor closing and sealing said other end.

3. A bag according to claim 2, in which said paper tube is ofa porous,fibrous paper so that the bag is usable as a dispoable dust containerfor a vacuum cleaner.

1. A bag comprising a paper tube which is flattened at least at one endand includes first substantially flat opposed panels connected at theirsides by second opposed panels which are creased to define pleatsdirected inwardly between said first panels at least at said flattenedend, and an elongated, selfsupporting enveloping cap of thermoplasticmaterial extending across said one end and having adjacent end edges ofone of said first panels and said pleats embedded in, and secured toeach other by said cap, the other of said first panels having its endedge at said one end of the tube spaced, in the longitudinal directionof the tube, from said adjacent end edges of said one first panel andsaid pleats so that said end edge of said other first panel is free ofsaid thermoplastic cap and the latter holds said pleats closed at therespective end of said tube for providing a restricted opening to thebag.
 1. A bag comprising a paper tube which is flattened at least at oneend and includes first substantially flat opposed panels connected attheir sides by second opposed panels which are creased to define pleatsdirected inwardly between said first panels at least at said flattenedend, and an elongated, self-supporting enveloping cap of thermoplasticmaterial extending across said one end and having adjacent end edges ofone of said first panels and said pleats embedded in, and secured toeach other by said cap, the other of said first panels having its endedge at said one end of the tube spaced, in the longitudinal directionof the tube, from said adjacent end edges of said one first panel andsaid pleats so that said end edge of said other first panel is free ofsaid thermoplastic cap and the latter holds said pleats closed at therespective end of said tube for providing a restricted opening to thebag.
 2. A bag according to claim 1, in which end edges of both of saidfirst panels and all of said pleats at the other end of said tube areembedded in an additional elongated, self-supporting enveloping cap ofthermoplastic material which extends across said other end of the tubefor closing and sealing said other end.